53BP1 expression is a modifier of the prognostic value of lymph node ratio and CA 19-9 in pancreatic adenocarcinoma

Ausborn et al. BMC Cancer 2013, 13:155
/>
RESEARCH ARTICLE

Open Access

53BP1 expression is a modifier of the prognostic
value of lymph node ratio and CA 19–9 in
pancreatic adenocarcinoma
Natalie L Ausborn1, Tong Wang1, Sabrina C Wentz2, Mary Kay Washington2, Nipun B Merchant3, Zhiguo Zhao4,
Yu Shyr4, Anuradha Bapsi Chakravarthy1 and Fen Xia5*

Abstract
Background: 53BP1 binds to the tumor suppressor p53 and has a key role in DNA damage response and repair.
Low 53BP1 expression has been associated with decreased survival in breast cancer and has been shown to
interact with several prognostic factors in non-small cell lung cancer. The role of 53BP1 in pancreatic ductal
adenocarcinoma (PDAC) has yet to be determined. We aimed to investigate whether 53BP1 levels interact with
established prognostic factors in PDAC.
Methods: 106 patients for whom there was tissue available at time of surgical resection for PDAC were included. A
tissue microarray was constructed using surgical specimens, stained with antibodies to 53BP1, and scored for
expression intensity. Univariate and multivariate statistical analyses were performed to investigate the association
between 53BP1 and patient survival with known prognostic factors for survival.
Results: The association of 53BP1 with several established prognostic factors was examined, including stage, tumor
grade, surgical margin, peripancreatic extension, lymph node ratio (LNR), and CA 19–9. We found that 53BP1
modified the effects of known prognostic variables including LNR and CA 19–9 on survival outcomes. When 53BP1
intensity was low, increased LNR was associated with decreased OS (HR 4.84, 95% CI (2.26, 10.37), p<0.001) and high
CA19-9 was associated with decreased OS (HR 1.72, 95% CI (1.18, 2.51), p=0.005). When 53BP1 intensity was high,
LNR and CA19-9 were no longer associated with OS (p=0.958 and p=0.606, respectively).
Conclusions: In this study, 53BP1, a key player in DNA damage response and repair, was found to modify the
prognostic value of two established prognostic factors, LNR and CA 19–9, suggesting 53BP1 may alter tumor
behavior and ultimately impact how we interpret the value of other prognostic factors.

Keywords: BRCA1 protein, 53BP1, Pancreatic cancer, DNA damage, Repair

Background
Pancreatic ductal adenocarcinoma (PDAC) is the fourth
leading cause of cancer death in the United States and
continues to have a dismal prognosis, with a 5-year overall survival rate less than 4% [1]. The only potential
curative option is surgical resection, for which less than
20% of patients are eligible. Even in this subset of patients, the 5-year overall survival remains only 18–24%
[2-6]. Given the poor survival with surgery alone,
* Correspondence:
5
Department of Radiation Oncology, The Ohio State University College of
Medicine, Starling Loving, 300 W 10th Avenue, Columbus, OH 43210, USA
Full list of author information is available at the end of the article

attempts have been made to improve outcomes with adjuvant therapy. In multiple retrospective studies,
chemoradiation therapy has been shown to confer a survival advantage compared with surgical resection alone
[2,7,8]. Other studies suggest a benefit to adjuvant
chemotherapy alone and not to adjuvant chemoradiation
therapy [9-11]. The role of adjuvant therapy in the management of localized pancreatic cancer remains controversial as many of the randomized clinical trials were
statistically underpowered and used outdated radiation
fractionation schema and techniques. Therefore, tumor
biomarkers that could be used to predict which subset
of patients is likely to benefit from adjuvant therapy

© 2013 Ausborn et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License ( which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

Ausborn et al. BMC Cancer 2013, 13:155
/>
would be useful for clinicians to tailor therapy based on
that individual patient’s tumor characteristics.
Many chemotherapeutic agents act by inducing DNA
damage within rapidly dividing tumor cells. Ionizing radiation also causes DNA damage by inducing double-strand
breaks (DSBs), which results in cell death. Molecular targets that regulate DNA damage and repair are hence likely
to be good predictors of prognosis and response to treatment. The p53 binding protein 1 (53BP1) is a key mediator of DNA damage response, as it is a critical transducer
of the DNA damage signal to p53 and other tumor suppressors [12]. DNA DSBs are typically repaired by two
major pathways: template-based homologous recombination (HR) and nontemplate-based nonhomologous end
joining (NHEJ) [13]. 53BP1 plays a key role in promoting
the use of NHEJ to repair lethal DSBs [14]. Poly-(ADPribose) polymerase (PARP) is a key nuclear enzyme in
DNA single-strand break repair whose inhibition induces
synthetic lethality in BRCA1-mutated tumor cells which
are HR deficient [15,16]. DNA double-strand breaks in
BRCA1Δ11/Δ11 cells, which are deficient in HR, are aberrantly joined by NHEJ dependent on 53BP1 [17]. Interestingly, deletion of 53BP1 in BRCA1Δ11/Δ11 cells restored
HR and alleviated hypersensitivity of BRCA1-mutated cells
to PARP inhibition, rendering BRCA1Δ11/Δ11 cells insensitive to PARP inhibition [17]. In another study, Bouwman
et al. found that 53BP1 deletion reversed cisplatin sensitivity induced by BRCA1 inactivation [18]. Thus, 53BP1 expression may be a good predictor of pancreatic tumor
response to DNA damage-based therapy.
Additionally, low 53BP1 expression has been shown to
be associated with poor prognosis. Bouman et al. found
that loss of 53BP1 was associated with poor prognosis in
patients with triple-negative breast cancer [18]. The role
of 53BP1 in PDAC is yet to be determined. In this study,
we investigate whether 53BP1 protein expression level is
associated with pancreatic tumor behavior and how it interacts with other established prognostic factors in PDAC.

Methods
Patient selection and data collection

This study was approved by the Vanderbilt University
Medical Center Institutional Review Board. 106 patients
were identified who had undergone curative resections
for pancreatic adenocarcinoma and for whom both clinical data and tumor tissue were available. Only patients
with histologically confirmed ductal adenocarcinomas
were included. All tumors were restaged by a single
pathologist (SCW) according to AJCC 7th edition criteria
[19]. Data collected included patient demographics, operative details, treatment details and survival. Pathologic
data obtained included tumor location, total number of
nodes involved, total number of nodes resected, tumor
size, differentiation, pancreatic extension, and margin

Page 2 of 8

status. A positive margin was defined as tumor within 1
mm of the inked resection margin on microscopic examination. The assessment of margins and slicing techniques
were performed in a standardized fashion for all patients
as previously described [20]. Tumor differentiation was
recorded according to the guidelines outlined by the College of American Pathologists [21]. The lymph node ratio
(LNR) was defined as the number of positive lymph nodes
as a fraction of the total number of lymph nodes examined. CA 19–9 level was determined by a quantitative
electrochemiluminescent immunoassay (Roche Modular
E170) with a reference interval of 0–37 U/mL.
Construction of tissue microarray

Tissue microarrays were constructed using 1 mm cores
of both tumor and background normal/reactive pancreas from 106 curative resection specimens, including
pancreaticoduodenectomy/gastrojejunostomy procedures
(Whipple procedures) and total or distal pancreatectomies. The microarrays were composed of single or duplicate cores from tumor and background pancreas. The

microarrays were cut at 5 μm-thickness and stained with
hematoxylin and eosin.
Immunohistochemistry study

5 μm-thick sections of formalin-fixed, paraffin-embedded
tissue microarrays were de-paraffinized and rehydrated.
Samples were pretreated to promote antigen retrieval with
Target Retrieval Solution (DAKO, Carpinteria, CA, USA).
Sections were blocked with 3% hydrogen peroxide, followed
by blocking in 2% goat serum/0.1% Triton-X 100/PBS
(1 hour). Slides were then incubated with primary antibody
53BP1 (1:200 dilution in blocking buffer, NOVUS, Cat.
No. NB100-304) overnight at 4°C. Slides were washed
in phosphate-buffered saline. DAB (3,3-diaminobenzidine
tetrahydrochloride dehydrate, Invitrogen, Cat. No. 00–
2020) was applied. 53BP1 expression was analyzed by
microscopy (Carl Zeiss, Thornwood, NY).
Positive and negative controls were established with the
use of human breast cancer cells and a human breast
tumor specimen. The MCF-7 cell line, which is derived
from human breast cancer and expresses 53BP1 as confirmed by us and other research laboratories [22], was first
used to perform 53BP1 antibody immunostaining. The
MCF7 cells were not paraffin imbedded and were instead
cultured as a monolayer in a tissue culture chamber prior
to immunostaining. For a positive control, cells were
stained with antibody to 53BP1 as described above. For a
negative control, the primary antibody was not used and
instead was replaced by non-immune rabbit IgG at the
same concentration of the primary antibody. We obtained
positive staining in the positive control and negative staining in the negative control. Next, 53BP1 immunostaining

was performed in a human cancer tumor specimen. A


Ausborn et al. BMC Cancer 2013, 13:155
/>
human breast tumor specimen was used because breast
tumors have been reported to have positive 53BP1 expression [23,24]. 5 μm-thick consecutive sections of formalinfixed, paraffin-embedded breast cancer tissue were deparaffinized and rehydrated as described above. Tissue was
stained with antibody to 53BP1. For a negative control, a
consecutive section from the same specimen was not
stained with the primary 53BP1 antibody and instead was
replaced by non-immune rabbit IgG at the same concentration of the primary antibody. The immune-staining specificity of the 53BP1 antibody was confirmed by no staining in
the negative control which omitted the primary 53BP1 antibody and positive staining in the specimen to which the
primary antibody was applied. For each pancreatic cancer
tissue microarray, a total of 300–450 cells were counted.
The intensity of staining was scored as 1+ (weakly staining/
least intense), 2+ (moderately staining), or 3+ (strongly
staining/most intense) in tumor cells. Due to limited sample size, 1+ and 2+ staining intensity were grouped into
“low” intensity, and 3+ staining intensity was referred to as
“high” intensity. Stromal cells were not included in the
scoring. Assessment of 53BP1 staining was performed by a
single person blinded to patient outcomes. Representative
immunohistochemical staining is shown in Figure 1.

Page 3 of 8

OS) or last follow-up. The secondary endpoint was
defined as the time from surgery to the date of disease
recurrence (recurrence-free survival, RFS) or last followup. Patients’ demographic and clinical variables were
summarized using the median with the 25th and 75th
percentiles (interquartile range, IQR) for continuous variables. For categorical variables, frequency and percentages were shown. The Wilcoxon rank sum test was used

for continuous variables, and Pearson’s χ2 or Fisher’s
exact test was used to compare categorical variables
between 53BP1 intensity groups (low or high). The
Kaplan-Meier method, Log-rank test, likelihood ratio
test, and Cox proportional hazard (Cox PH) models
were used in univariate and multivariate analysis when
appropriate to investigate the associations between the
endpoints and the risk factors. Predetermined interactions of 53BP1 levels by LNR and 53BP1 levels by CA
19–9 levels were included in all multivariable models.
All statistical inferences were assessed at a two-sided 5%
significant level and all summary statistics, graphics, and
survival models were generated using R version 2.13
statistical software [25].

Results
Patient clinical and pathologic characteristics

Statistical analysis

The primary endpoint was defined as the time from
surgery to the date of all-cause death (overall survival,

106 patients were identified who had undergone curative
resections for PDAC for whom tissue samples were also
available for study. Table 1 summarizes the demographic

Figure 1 Representative immunohistochemistry staining for 53BP1 expression in pancreatic adenocarcinoma. (A) is high intensity of
53BP1 expression and (B) is low intensity of 53BP1 expression.

Ausborn et al. BMC Cancer 2013, 13:155
/>
Page 4 of 8

Table 1 Patient clinical and pathologic characteristics
N

No. (%)

Age, years

106

68 (58–73) a

Gender

106

Female

47 (44)

Male
Race

59 (56)
105

African American

6 (5.7)

Caucasian

99 (94.3)

Tumor grade

106

and treatment details as well as clinicopathologic findings. Of the 106 patients undergoing surgical resection,
71.0% had microscopically negative surgical margins.
The median OS for all patients was 15.5 (IQR: 8.2–35.4)
months.
Univariate analysis

53BP1 staining intensity was not found to be associated
with OS or RFS (p>0.05). 53BP1 intensity was not found
to be associated with tumor stage, tumor grade, adjuvant
chemotherapy use, CA 19–9 level, or LNR (p>0.05).
Findings are summarized in Table 2.

1

15 (14)

2

62 (58)

Multivariable analysis

3

29 (27)

Recent molecular correlative studies in glioblastoma
have shown that certain molecules can modify the value
of other prognostic biomarkers [26]. Although 53BP1 intensity was not associated with any of the known prognostic factors in univariate analysis, we postulated that
53BP1 expression levels could interact with and thereby
modify established prognostic markers in PDAC. Lymph
node involvement in PDAC predicts for worse survival.
Carbohydrate 19–9 antigen (CA 19–9) is a sensitive and
specific biomarker for pancreatic cancer. The total CA
19–9 values as well as the rates of decline have been
shown to predict survival in patients with advanced disease [27-31].
In multivariable analysis, we observed that 53BP1 intensity modifies the prognostic ability of both LNR and
CA19-9. When 53BP1 intensity is low, increased LNR
was associated with decreased OS (HR 4.84, 95% CI
(2.26, 10.37), p<0.001) and high CA19-9 was associated
with decreased OS (1.72, (1.18, 2.51), p=0.005). When
53BP1 intensity is high, LNR and CA19-9 were not

Tumor stage

106

I-IIA

31 (29)

IIB-IV

75 (71)

Tumor size

106

Lymph node status (N stage)

104

N0

3.0 (2.1–3.5) a

35 (34)

N1

69 (66)

Number of resected nodes

104

11.0 (8.0–18.2) a

Number of positive nodes

104

1.0 (0.0–4.0) a

Lymph node ratio

104

0.095 (0.000–0.257) a

Operation type

106

Whipple

93 (87.7)

Distal pancreatectomy

9 (8.5)

Total pancreatectomy

3 (2.8)

En bloc resection
Surgical margin status

1 (1)
106

Negative

75 (71)

Positive

31 (29)

Adjuvant chemotherapy
No

27 (26)

Yes

75 (74)

Adjuvant radiation therapy

102

No

50 (49)

Yes

52 (51)

CA 19-9

106

53BP1 expression intensity

106

157 (50–520) a

Low intensity

62 (58)

High intensity

44 (42)

Overall survival status

106

Alive

23 (22)

Deceased

83 (78)

Survival time, months
a

: median (IQR).

Table 2 Univariate analysis of 53BP1 expression intensity

102

106

15.5 (8.2–35.4) a

Low intensity
(N=62), No. (%)

High intensity
(N=44), No. (%)

Tumor grade
1

8 (13%)

7 (16%)

2

36 (58%)

26 (59%)

3

18 (29%)

11 (25%)

Tumor stage
I-IIA

18 (29%)

13 (30%)

IIB-IV

44 (71%)

31 (70%)

No

16 (27%)

Yes

44 (73%)

Lymph node ratio
a

: Fisher’s Exact Test.
: Wilcoxon Rank Sum Test.
1
: Median (IQR).
b

0.85

a

0.98

a

1a

Adjuvant chemotherapy

CA 19-9

p-value

210 (66–660)

11 (26%)

31 (74%)
1

0.10 (0.00–0.25)

112 (32–337)1
1

0.09 (0.00–0.27)

1

0.12

b

0.92

b


Ausborn et al. BMC Cancer 2013, 13:155
/>
Page 5 of 8

associated with OS (p=0.958 and p=0.606, respectively).
When 53BP1 intensity was low, increased LNR was also
associated with decreased RFS (3.92, (1.79, 8.58),
p<0.001) and high CA 19–9 had a trend towards decreased RFS that did not reach statistical significance
(1.38, (0.97, 1.96), p=0.077). Results are summarized in

Table 3. Hazards ratios are shown in Figure 2.

Discussion
In this study, 53BP1 was found to modify the effect of
two established pancreatic cancer clinicopathological
prognostic factors, LNR and CA 19–9 level, on patient
survival.
The number of nodes involved is a function not only
of the rates of true node positivity but also of the aggressiveness of the surgeon in obtaining these nodes and the
pathologist in finding these nodes at the time of resection. Adequate staging of node negative pancreatic cancer requires the evaluation of at least 12 nodes.
Unfortunately, this is not always feasible. The ratio of
number of positive nodes to the number of nodes examined or the LNR help to equalize these variations in both
surgical technique as well as pathological nodal evaluation. LNR has been shown to be of prognostic value in
a variety of gastrointestinal tumors including cancers of
the stomach, esophagus, colon, rectum, and biliary tract
[32-36] and has been suggested as an important prognostic factor in pancreatic cancer as well [37-40]. However, the current determination of N stage in pancreatic
cancer is delineated as either positive or negative, rather
than the absolute number of nodes or LNR. In our
study, we found that when 53BP1 intensity was low,

increased LNR was associated with decreased OS (HR
4.84, p<0.001) and RFS (HR 3.92, p<0.001). However, the
association of LNR with survival was lost when 53BP1
intensity was high, suggesting that 53BP1 may modulate
the tumor cellular environment where low 53BP1 expression level causes worse prognosis for high LNR.
CA 19–9, a sialylated Lewis (Lea) antigen of the
MUC1 protein, is another prognostic marker in pancreatic cancer, and serial measurements of CA 19–9 have
been shown to be useful to monitor treatment response
[41,42]. There are several studies that have evaluated CA
19–9 as a pretreatment prognostic marker [27-31], and

although there is no established threshold value for
prognostic evaluation, 370 U/ml has been found to divide patients into two groups with a significant difference
in survival [43]. In our study, we found that when 53BP1
intensity was low, high CA19-9 was associated with decreased OS (HR 1.72, p=0.005). When 53BP1 intensity
was high, CA 19–9 was no longer associated with overall
survival.
Taken together, our results suggest 53BP1 expression
levels may precondition the tumor cell biological behavior.
53BP1, as a DNA damage response protein, is thought to
promote NHEJ and suppress HR [14]. Increased 53BP1
levels therefore likely allows efficient cellular repair of endogenous DNA damage in response to metabolic stress or
chemotherapy and radiation therapy; however, when
53BP1 levels are decreased, there is decreased NHEJ efficiency to repair DNA damage. Our data suggest that low
53BP1 expression may predispose pancreatic tumor cells
to become more vulnerable to changes of intrinsic metabolic stress, tumor microenvironment, and genotoxic

Table 3 Multivariable Cox PH analyses for OS and RFS
Overall survival
Variables
Age at surgery

1, a

95% CI

p value

HR

95% CI

p value

1.27

0.84–1.91

0.255

1.00

0.67–1.48

0.982

0.007 b,*

1.02
3.92

Lymph node ratio
Within High 53BP1 level strata 2,
Within Low 53BP1 level strata

a

2, a

0.98

0.43–2.22

0.958

4.84

2.26–10.37

<0.001*

Within Low 53BP1 level strata

0.020 b,*
0.45–2.29

0.963

1.79–8.58

<0.001*

0.040 b,*

CA19-9
Within High 53BP1 level strata

Recurrence free survival

HR

3, a
3, a

Adjuvant chemotherapy: Yes

0.87

0.52–1.47

0.606
*

0.226 b
0.94

0.56–1.57

0.803

1.72

1.18–2.51

0.005

1.38

0.97–1.96

0.077

0.34

0.19–0.60

<0.001*

0.55

0.30–1.00

0.051

*

Margin Positive

2.37

1.35–4.14

0.003

1.36

0.75–2.47

0.316

Peripancreatic extension status Positive

2.29

1.12–4.65

0.022*

2.41

1.16–5.01

0.019*

Perineural invasion status Positive

0.52

0.29–0.95

0.033*

0.46

0.25–0.81

0.008*

a

: upper quartile vs. lower quartile.

: P value for interaction terms with 53BP1 Level.
1
: 73.10 vs. 58.38.
2
: 25.69% vs. 0%.
3
: 519.75 vs. 50.
*
: statistically significant.
b


Ausborn et al. BMC Cancer 2013, 13:155
/>
Page 6 of 8

Hazard Ratios

A.
Age at surgery(73.10 vs. 58.38)

Lymph node ratio in low 53BP1 strata(0.26 vs. 0.00)

CA19 9 in low 53BP1 strata(519.75 vs. 50.00)

Lymph node ratio in high 53BP1 strata(0.26 vs. 0.00)

CA19 9 in high 53BP1 strata(519.75 vs. 50.00)

Chemotherapy Yes

Margin status Positive

Perineural invasion status Positive

Peripancreatic extension status Positive

0

2

4

B.

6

8

10

Hazard Ratios
Age at surgery(73.10 vs. 58.38)

Lymph node ratio in low 53BP1 strata(0.26 vs. 0.00)

CA19 9 in low 53BP1 strata(519.75 vs. 50.00)

Lymph node ratio in high 53BP1 strata(0.26 vs. 0.00)

CA19 9 in high 53BP1 strata(519.75 vs. 50.00)

Chemotherapy Yes

Margin status Positive

Perineural invasion status Positive

Peripancreatic extension status Positive

0

2

4

6

8

Figure 2 Hazard ratios for clinical and pathologic characteristics for (A) OS and (B) RFS.

stress from DNA damage based therapy. In turn this could
modify how other prognostic factors such as LNR and
CA19-9 predict overall survival.
In a cohort of breast cancer patients treated with
breast-conserving surgery and radiotherapy, low 53BP1
was associated with worse clinical outcomes including
recurrence-free survival, distant metastasis-free survival,
and overall survival [24]. Bouman et al. found that 53BP1

loss was associated with the poor prognosis triple-negative
breast cancers [18]. 90.5% of breast tumors that were deficient in 53BP1 were triple-negative. Of the triple-negative
tumors assayed, 43% were 53BP1 negative and in non-triplenegative tumors, only 2% were 53BP1 negative (p<0.0001).
Together, this data suggests 53BP1 loss is more frequent in
more aggressive breast cancers. While in our study low
53BP1 was not directly associated with overall survival,
low 53BP1 expression modified the prognostic value of CA
19–9 and LNR so that high CA 19–9 and high LNR were

associated with worse OS. With high 53BP1, LNR and CA
19–9 were no longer associated with overall survival. One
study has shown an association between 53BP1 and
established lung cancer prognostic factors, such as smoking
status, lymphovascular invasion, and tumor stage [44].
Due to study size limitation, our study was unable to
test whether 53BP1 could modify the effects of other
clinicopathological factors such as adjuvant chemotherapy, margin status, peripancreatic extension status, and
perineural invasion status. For example, based on the
biologic function of 53BP1, 53BP1 may modify the prognostic value of adjuvant chemotherapy such as the use
of PARP inhibitors due to the ability of 53BP1 to alter
homologous recombination (HR) and nonhomologous
end joining (NHEJ). Loss of this protein may result in
the inability of cells to repair damaged DNA and modify
sensitivity to chemotherapeutic agents. Also, an important question not addressed in our study that should be


Ausborn et al. BMC Cancer 2013, 13:155
/>
addressed in a larger study is the relationship between
any of the clinicopathologic factors and local recurrence

or distant metastasis.
There are several limitations to our study. For instance, our study group is heterogenous in that patients
were included regardless of type of surgical procedure,
and the number of lymph nodes retrieved may vary considerably among those procedures. In order to increase
our sample size all patients were included. Additionally,
in our study perineural invasion was found to have a
positive impact on survival, which is inconsistent with
the literature. Our finding may be the result of small
numbers and the retrospective nature of tissue collection. Our study found that CA 19–9, positive margin,
and adjuvant chemotherapy were associated with OS but
not RFS. The lack of association with RFS may be a
function of the difficulty of accurately coding of recurrence in a retrospective study that spanned such a long
time period. Therefore, our hypothesis should be tested
with prospectively collected tissue in a large cooperative
group setting.
Future studies are warranted to further characterize
the role of 53BP1 in PDAC as well as to study the mechanisms by which 53BP1 intensity affects tumor cell behavior. Our results point to the complexity of the
translation of cancer cell biology to clinical tumor behavior. A hallmark of cancer cells is the possession of
multiple gene mutations and aberrations in cell signaling
pathways. The ability to identify a single biomarker to
predict tumor response has been disappointing. There
will always be an interaction with additional biomarkers
or clinicopathological factors. Therefore, it is necessary
to interpret the predictive value of a particular biomarker in light of the status of other biomarkers in that
individual tumor. Stratification of tumors based on the
summation of several biomarkers and clinicopathological
factors will allow for better predictive value in the clinic.
As the role of 53BP1 in tumors has been shown in several studies to modify the sensitivity of BRCA-mutated
cells to chemotherapeutic agents (PARP inhibitors, cisplatin) [17,18], future studies examining the role of
53BP1 in BRCA-mutated pancreatic cancer would be of

clinical value.

Conclusion
In summary, our results demonstrate 53BP1 modifies
the effect of two established pancreatic prognostic factors, LNR and CA 19–9, suggesting 53BP1 may alter
tumor behavior and ultimately impact how we interpret
the clinical value of other prognostic factors.
Abbreviations
PDAC: Pancreatic ductal adenocarcinoma; DSBs: Double-strand breaks;
53BP1: P53 binding protein 1; HR: Homologous recombination;
NHEJ: Nonhomologous end joining; PARP: Poly-(ADP-ribose) polymerase;

Page 7 of 8

LNR: Lymph node ratio; OS: Overall survival; RFS: Recurrence-free survival;
IQR: Interquartile range; CA 19–9: Carbohydrate 19–9 antigen.
Competing interests
Nipun Merchant has received honoraria from Covidien and Medtronics 2012
and Advisory Board for Biocompatibles, Inc., 2012. Fen Xia has received
honoria from Abbott, 2011. All remaining authors have declared no conflicts
of interest.
Authors’ contributions
NLA carried out data collection, assisted in data interpretation, and drafted
the manuscript. TW carried out immunohistochemistry and assisted in data
collection. SCW determined tumor staging and assisted in data collection.
MKW participated in the data collection and coordination of the study. NBM
assisted in coordination of the study and revision of the manuscript. ZZ and
YS performed the statistical analysis and aided in data interpretation. ABC
participated in the design of the study, data interpretation, and revision of
the manuscript. FX conceived of the study, participated in its design and

coordination, and helped to draft and revise the manuscript. All authors read
and approved the final manuscript.
Acknowledgements
This work was supported in part by the Tissue Core of the Vanderbilt SPORE
in GI Cancer (National Institutes of Health P50CA095103), in part by the
Vanderbilt-Ingram Cancer Center Support Grant (National Institutes of Health
P30 CA68485), and in part by the Vanderbilt Clinical and Translational
Science Award grant (UL1 RR024975-01).
Author details
1
Department of Radiation Oncology, Vanderbilt University School of
Medicine, Nashville, TN, USA. 2Department of Pathology, Vanderbilt University
School of Medicine, Nashville, TN, USA. 3Department of Surgery, Vanderbilt
University School of Medicine, Nashville, TN, USA. 4Department of
Biostatistics, Vanderbilt University School of Medicine, Nashville, TN, USA.
5
Department of Radiation Oncology, The Ohio State University College of
Medicine, Starling Loving, 300 W 10th Avenue, Columbus, OH 43210, USA.
Received: 25 September 2012 Accepted: 8 March 2013
Published: 26 March 2013
References
1. Siegel R, Naishadham D, Jermal A: Cancer statistics, 2012. CA Cancer J Clin
2012, 62:10–29.
2. Yeo CJ, Abrams RA, Grochow LB, et al: Pancreaticoduodenectomy for
pancreatic adenocarcinoma: postoperative adjuvant chemoradiation
improves survival. A prospective, single-institution experience. Ann Surg
1997, 225:621–633.
3. Sohn TA, Yeo CJ, Cameron JL, et al: Resected adenocarcinoma of the
pancreas-616 patients: results, outcomes, and prognostic indicators.
J Gastrointest Surg 2000, 4:567–579.

4. Cameron JL, Pitt HA, Yeo CJ, et al: One hundred and forty-five consecutive
pancreaticoduodenectomies without mortality. Ann Surg 1993, 217:430–438.
5. Balcom JH, Rattner DW, Warshaw AL, et al: Ten-year experience with 733
pancreatic resections: changing indications, older patients, and
decreasing length of hospitalization. Arch Surg 2001, 136:391–398.
6. Birkmeyer JD, Finlayson SR, Tosteson AN, et al: Effect of hospital volume on inhospital mortality with pancreaticoduodenectomy. Surgery 1999, 125:250–256.
7. Hsu CC, Herman JM, Corsini MM, et al: Adjuvant chemoradiation for
pancreatic adenocarcinoma: the Johns Hopkins Hospital-Mayo Clinic
collaborative study. Ann Surg Oncol 2010, 17:981–990.
8. Corsini MM, Miller RC, Haddock MG, et al: Adjuvant radiotherapy and
chemotherapy for pancreatic carcinoma: the Mayo Clinic experience
(1975–2005). J Clin Oncol 2008, 26:3511–3516.
9. Klinkenbijl JH, Jeekel J, Sahmoud T, et al: Adjuvant radiotherapy and
5-fluorouracil after curative resection of cancer of the pancreas and
periampullary region: phase III trial of the EORTC gastrointestinal tract
cancer cooperative group. Ann Surg 1999, 230:776–782.
10. Neoptolemos JP, Dunn JA, Stocken DD, et al: Adjuvant chemoradiotherapy
and chemotherapy in resectable pancreatic cancer: a randomised
controlled trial. Lancet 2001, 358:1576–1585.


Ausborn et al. BMC Cancer 2013, 13:155
/>
11. Neoptolemos JP, Stocken DD, Friess H, et al: A randomized trial of
chemoradiotherapy and chemotherapy after resection of pancreatic
cancer. N Engl J Med 2004, 350:1200–1210.
12. Wang B, Matsuoka S, Carpenter PB, Elledge S: 53BP1, a mediator of the
DNA damage checkpoint. Science 2002, 298:1435–1438.
13. Moynahan ME, Jasin M: Mitotic homologous recombination maintains genomic
stability and suppresses tumorigenesis. Nat Rev Mol Cell Biol 2010, 11:196–207.

14. Xie A, Hartlerod A, Stucki M, et al: Distinct roles of chromatin-associated
proteins MDC1 and 53BP1 in mammalian double-strand break repair.
Mol Cell 2007, 28:1045–1057.
15. Banerjee S, Kaye S: PARP inhibitors in BRCA gene-mutated ovarian cancer
and beyond. Curr Oncol Rep 2011, 13:442–449.
16. Comen EA, Robson M: Poly(ADP-ribose) polymerase inhibitors in triplenegative breast cancer. Cancer K 2010, 16:48–52.
17. Bunting SF, Callen E, Wong N, et al: 53BP1 inhibits homologous
recombination in Brca1-deficient cells by blocking resection of DNA
breaks. Cell 2010, 141:243–254.
18. Bouwman P, Aly A, Escandell JM, et al: 53BP1 loss rescues BRCA1
deficiency and is associated with triple-negative and BRCA-mutated
breast cancers. Nat Struct Mol Biol 2010, 17:688–695.
19. Edge SB, Byrd DR, Compton CC, et al: AJCC Cancer Staging Manual. 7th
edition. New York: Springer; 2010.
20. Westra WH, Hruban RH, Phelps TH, Isacson C: Pancreas, Surgical Pathology
Dissection: An Illustrated Guide. 2nd edition. New York: Springer; 2003:88–92.
21. College of American Pathologists Cancer: Protocol for the examination of
specimens from patients with carcinoma of the exocrine pancreas.
[ />PancreasExo_11protocol.pdf].
22. Karimi-Busheri F, Rasouli-Nia A, Mackey JR, et al: Senescence evasion by
MCF-7 human breast tumor-initiating cells. Breast Cancer Res 2010, 12:R31.
23. Grotsky DA, Gonzalez-Suarez I, Novell A, et al: BRCA1 loss activates
cathepsin L–mediated degradation of 53BP1 in breast cancer cells. J Cell
Biol 2013, 200:187–202. Reference 23 in revised manuscript.
24. Neboori HJR, Haffty BG, Wu H, et al: Low p53 binding protein 1 (53BP1)
expression is associated with increased local recurrence in breast cancer
patients treated with breast-conserving surgery and radiotherapy.
Int J Radiat Oncol Biol Phys 2012, 83:c677–c683.
25. R Development Core Team: A language and environment for statistical
computing. Vienna, Austria: R Foundation for Statistical Computing; 2011.

26. Prados MD, Chang SM, Butowski N, et al: Phase II study of erlotinib plus
temozolomide during and after radiation therapy in patients with newly
diagnosed glioblastoma multiforme or gliosarcoma. J Clin Oncol 2009,
27:579–584.
27. Smith RA, Bosonnet L, Ghaneh P, et al: Preoperative CA19-9 levels and
lymph node ratio are independent predictors of survival in patients with
resected pancreatic ductal adenocarcinoma. Dig Surg 2008, 25:226–232.
28. Kondo N, Murakami Y, Uemura K, et al: Prognostic impact of perioperative
serum CA 19–9 levels in patients with resectable pancreatic cancer. Ann
Surg Oncol 2010, 17:2321–2329.
29. Ikeda M, Okada S, Tokuuye K, et al: Prognostic factors in patients with
locally advanced pancreatic carcinoma receiving chemoradiotherapy.
Cancer 2001, 91:490–495.
30. Micke O, Bruns F, Kurowski R, et al: Predictive value of carbohydrate
antigen 19–9 in pancreatic cancer treated with radiochemotherapy. Int J
Radiat Oncol Biol Phys 2003, 57:90–97.
31. Saad ED, Machado MC, Wajsbrot D, et al: Pretreatment CA 19–9 level as a
prognostic factor in patients with advanced pancreatic cancer treated
with gemcitabine. Int J Gastrointest Cancer 2002, 32:35–41.
32. Berger AC, Sigurdson ER, LeVoyer T, et al: Colon cancer survival is
associated with decreasing ratio of metastatic to examined lymph
nodes. J Clin Oncol 2005, 23:8706–8712.
33. Inoue K, Nakane Y, Iiyama H, et al: The superiority of ratio-based lymph
node staging in gastric carcinoma. Ann Surg Oncol 2002, 9:27–34.
34. Negi SS, Singh A, Chaudhary A: Lymph nodal involvement as prognostic
factor in gallbladder cancer: location, count or ratio? J Gastrointest Surg
2011, 15:1017–1025.
35. Nitti D, Marchet A, Olivieri M, et al: Ratio between metastatic and
examined lymph nodes is an independent prognostic factor after D2
resection for gastric cancer: analysis of a large European

monoinstitutional experience. Ann Surg Oncol 2003, 10:1077–1085.

Page 8 of 8

36. Wijnhoven BP, Tran KT, Esterman A, et al: An evaluation of prognostic
factors and tumor staging of resected carcinoma of the esophagus. Ann
Surg 2007, 245:717–725.
37. Berger AC, Watson JC, Ross EA, Hoffman JP: The metastatic/examined
lymph node ratio is an important prognostic factor after
pancreaticoduodenectomy for pancreatic adenocarcinoma. Am Surg
2004, 70:235–240.
38. Pawlik TM, Gleisner AL, Cameron JL, et al: Prognostic relevance of lymph
node ratio following pancreaticoduodenectomy for pancreatic cancer.
Surgery 2007, 141:610–618.
39. Riediger H, Keck T, Wellner U, et al: The lymph node ratio is the strongest
prognostic factor after resection of pancreatic cancer. J Gastrointest Surg
2009, 13:1337–1344.
40. House MG, Gonen M, Jarnagin WR, et al: Prognostic significance of
pathologic nodal status in patients with resected pancreatic cancer.
J Gastrointest Surg 2007, 11:1549–1555.
41. Willett CG, Daly WJ, Warshaw AL: CA 19–9 is an index of response to
neoadjunctive chemoradiation therapy in pancreatic cancer. Am J Surg
1996, 172:350–352.
42. Abrams RA, Grochow LB, Chakravarthy A, et al: Intensified adjuvant
therapy for pancreatic and periampullary adenocarcinoma: survival
results and observations regarding patterns of failure, radiotherapy dose
and CA19-9 levels. Int J Radiat Oncol Biol Phys 1999, 44:1039–1046.
43. Lundin J, Roberts PJ, Kuusela P, Haglund C: The prognostic value of
preoperative serum levels of CA 19–9 and CEA in patients with
pancreatic cancer. Br J Cancer 1994, 69:515–519.

44. Lai TC, Chow KC, Lin TY, et al: Expression of 53BP1 as a cisplatin-resistant
marker in patients with lung adenocarcinomas. Oncol Rep 2010, 24:321–328.
doi:10.1186/1471-2407-13-155
Cite this article as: Ausborn et al.: 53BP1 expression is a modifier of the
prognostic value of lymph node ratio and CA 19–9 in pancreatic
adenocarcinoma. BMC Cancer 2013 13:155.

Submit your next manuscript to BioMed Central
and take full advantage of:
• Convenient online submission
• Thorough peer review
• No space constraints or color figure charges
• Immediate publication on acceptance
• Inclusion in PubMed, CAS, Scopus and Google Scholar
• Research which is freely available for redistribution
Submit your manuscript at
www.biomedcentral.com/submit